In 597, a party of forty missionary monks, led by St Augustine of Canterbury (May 28), was sent to Britain by the holy Pope Gregory the Great, to bring the blessed Gospel of Jesus Christ to the English people. Aethelberht, who had been King of Kent for thirty-six years, received the monks favorably, allowed them to preach in his kingdom, and invited them to establish their headquarters in Canterbury, his capital city, which already contained a small, ruined church dedicated to St Martin of Tours in Roman times.

The king himself was converted and received holy Baptism at the hands of St Augustine; a crowd of his subjects followed his example. When St Augustine was consecrated bishop, Aethelberht allowed him to be made Archbishop of Canterbury and gave his own palace to serve as a monastery. The king worked steadily for the conversion of the neighboring kindoms, and in 604 established an episcopal see in London. Unlike some Christian rulers, he refused to see anyone converted forcibly.

Saint Aethelberht reposed in peace in 616, after reigning for fifty-six years. He was buried in the Church of Saints Peter and Paul, which he had established. Many miracles were worked at his tomb, where a lamp was kept lit perpetually until the monastery was disbanded by the Protestants in 1538.